1. Field of the Invention
The present invention concerns a filter for molten metal comprising at least two refractory material plates in contact with each other at their periphery, defining between them one or more cavities and each comprising a series of holes through which the liquid metal passes and by which the liquid metal is filtered.
2. Description of the Prior Art
A filter of this kind is described in French patent 2 593 077.
A filter of this kind can eliminate from the molten metal any solid inclusions such as metal oxides likely to affect the quality of the metal which is cast into a container such as a mold.
The effectiveness of a filter of this kind depends essentially on the diameter of the holes and the number of plates constituting it. The smaller the diameter of the holes the greater the ability of the filter to hold back fine inclusions and the more effective the filter action.
However, it is virtually impossible to carry out filtration using plates in which the holes are less than 1 mm in diameter.
Holes this size are difficult to make in a refractory or ceramic material such as cast alumina, for example.
Also, if the holes have a diameter less than 1 mm filtration takes a very long time (because the molten metal passes through holes this size with difficulty) and the holes quickly clog.
If the number of plates is increased the cost of the filter is increased.
It is known to place inside the aforementioned cavities a particulate filter material whose particles are larger than the diameter of the holes in the plate, at least in the case of the particles near a plate. The particles cannot pass through the holes and interstices are defined between them through which the molten metal to be filtered passes.
The above remarks concerning the diameter of the holes in the plates apply equally to the interstices between the particles.
An object of the present invention is to remedy the drawbacks of the above filters to create a more effective but economic filter.